While the invention is illustrated and described hereinbelow with reference to a self-pointing satellite antenna, the principles of the invention may be applied to antennas of similar construction used in other applications where it is desired to control or regulate the direction of the main beam of the antenna and/or from time-to-time make adjustments in the beam direction, either elevation, azimuth, or both.
In order to prevent interference and/or signal degradation, fixed earth station antennas must be pointed accurately at the satellite when installed and remain so during their operating lifetimes.
The normal method of mechanically scanning large antennas is to move the entire main reflector structure with large expensive jackscrews. Such designs demand expensive jacks, bearings and mounts to safely move large antennas in high winds. The invention is usable with large antennas with beamwidths so narrow that they must follow the satellite motion within normal fixed box limits of 0.1 degrees while meeting stringent gain and sidelobe requirements. Operation at larger angles can be accomplished, but with greater degradation of the signal strength and pattern sidelobes. The resultant fixed main reflector can be reinforced with struts to the ground or roof to withstand higher wind loads with less performance degradation.
Also, low-cost antennas for customer or “subscriber” premises, which may be deployed by the millions, are typically installed by relatively low-skill technicians and may be mounted to parts of residential structures which may shift enough to change the beam direction by more than the several tenths of a degree which is the acceptable limit for interactive applications. Conventional motorization of the antenna structure, i.e., motorizing the reflector mount to pivot and/or tilt the reflector in the azimuth and elevation planes would solve the problem, but is much too expensive to be practical.